Heating circuit control for electric appliances



April 8 1952 w. R. MoDowr-:LL 2,591,849

HEATING CIRCUIT CONTROL FOR ELECTRIC APPLIANCES Filed Dec. 3l. 1949 ecmng Unit 4Select Key Inventor Wolter R. Mc Dowell Bmzraawm Attys.

Patented Apr. s, 1952 HEATING CIRCUIT CONTROL FOR ELECTRIC APPLIANCES Walter R. McDowell, Western Springs, Ill., as-

signor to Hotpoint Inc., a corporation of New York Application December 31, 1949, Serial No. 136,365

16 Claims.

The present invention relates to heating circuit controls for electric appliances, and more particularly to improved circuit controls for electric ranges of the type disclosed in the copending application of Walter R. McDowell, Serial No. 56,813, led October 27, 1948, now Patent No. 2,550,579, granted on April 24, 1951.

In the McDowell application mentioned there is disclosed an electric range provided with a cooking top carrying a surface heating unit and a backsplasher carrying a manually operable control switch of the push button multiposition type for selectively setting the heating circuit connections between the heating unit and an associated source of alternating current of the three-wire Edison type. Also, this electric range comprises a cooking vessel carrying a thermal responsive device operative in response to a predetermined cooking condition in the vessel, an electro-responsive motor or relay operatively connected to the low push button of the control switch, and an operating circuit for the motor including the device.

In the operation of this electric range the high push button of the control switch is first manually operated to effect operation of the control switch from its oif position into its high position, and the vessel and its contents are placed upon the surface heating unit, whereby the vessel and its contents are heated at the high rate. Also, operation of the contro1 switch into its high position prepares the operating circuit for the motor; and when a cooking temperature is reached by the contents of the vessel, the thermal responsive device is operated automatically to close the operating circuit of the motor so as to effect operation thereof. Upon operating, the motor operates the low push button of the control switch in order to eieet operation of the control switch from its high position into its low position, whereby the vessel and its contents are further heated at the low rate. Also, operation of the control switch into its low position opens the operating circuit for the motor. The operation of the control switch from its high position into its low position in response to operation of the thermal responsive device prevents vigorous boiling of the contents of the vessel and assures continued cooking thereof at the low rate. Also, the control switch embodies an indicating arrangement for selectively illuminating the different operated ones of the push buttons thereof in corresponding colors, thereby to provide a color controlled indicator of the switching position of the contro1 switch.

While this heating control circuit arrangement is entirely satisfactory in operation, it provides facilities for selectively operating the control switch only upon the thermal basis noted; whereas, it has been found highly desirable to provide facility for operating the control switch also upon a time basis. In fact, it has been found most desirable to operate the control switch alternatively upon the thermal basis or upon a time basis under certain cooking conditions; and finally it has been found highly advantageous to operate the control switch sequentially iirst upon the thermal basis and then upon the time basis. Moreover, the arrangement of the McDowell application noted provides facility for operating only the contro1 switch associated with a particular one of the surface heating units, thereby limiting the general application of the arrangement to the utilization of this particular surface heating unit. In practice it has been found highly desirable to render this control facility suitably flexible so that it may be employed alternatively in conjunction with two of the surface heating units.

Accordingly, it is a general object of the present invention to provide in an electric Iheating appliance, such, for example, as an electric range, a heating control circuit arrangement that may be selectively or alternatively controlled either upon a thermal basis or upon a time basis.

Another object of the invention is to provide in an electric heating appliance, such, for example, as an electric range, a heating control circuit arrangement that may be selectively controlled sequentially rst upon a thermal basis and then upon a time basis. i

A further object of the invention is to provide in an electric heating appliance, such, for example, as an electric range, a heating contro1 circuit arrangement that may be selectively operatively associated with any one of a plurality of heating units incorporated in the range.

A still further object of the invention is to provide in an electric heating appliance, an improved heating contro1 circuit lending flexibility and ease of operation to the appliance.

Further features of the invention pertain to the particular arrangement of the elements of the electric heating appliance and of the control circuit incorporated therein, whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specication taken in connection with the accompanying drawing, in which the single figure is a diagrammatic illustration of the heating and control circuits and facilities incorporated in an electric range and embodying the present invention.

Referring now to the drawing, there is illustrated the heating control circuit for an electric range and embodying the features of the present invention. The electric range, not shown, comprises the usual cooking top provided with a pedestal adjacent to the rear thereof that supports the usual upstanding hollow backsplasher; all disclosed in the previously mentioned Mc- Dowell application. The control circuit comprises a plurality of surface heating units, including the rst surface heating unit i and the second surface heating unit HU. The surface heating units Il) and ||0 are disposed adjacent to the rear of the cooking top forwardly of the pedestal and the supported backsplasher, and preferably comprise the respective left rear and right rear surface heating units of the electric range. Preferably each of the heating units It and I I0 is of the usual sheathed resistance conductor type comprising two sections. Specifically, the heating unit IG comprises the series related sections and l2, and the heating unit comprises the series related sections and |2.

Also, the control circuit comprises a plurality -of manually operable control switches of the push button type, including the i'lrst control switch 2D and the second control switch |20. Preferably the control switches 2|) and |20 are of the basic construction of that disclosed in U. S. Patent No. 2,431,904, granted on December 2.11947 to John L. Andrews, and embody the color indicator arrangement disclosed in U. S. Patent No. 2,437,555, granted on March 9, 1948 to Gregory L. Rees. Each of the control switches comprises six individual switching positions and six corresponding push buttons, the switching positions and push buttons including high, second, third, low, warm and olf. Specifically, the control switch 2G comprises the six switching contacts 2|, 22, 23, 24, 25 and 2G that are selectively operated into the six switching positions noted by associated transfer and interlock mechanism 27 that is selectively operated by the associated six push buttons. Likewise, the control switch |23 comprises the six switching contacts |2|, |22, |23, |24, Y|25 and |26 that are selectively operated into the six switching positions noted by associated transfer and interlock mechanism |21 that is selectively operated by the associated six push buttons.

Also, the control circuit comprises an alternating current source of the three-wire Edison type including a line conductor, a neutral or N conductor and a line Conductor, the N conductor being grounded in the electric range, and a potential of 230 volts being present between the and the conductors, thereby providing a voltage of 115 volts between the N conductor and either of the other line conductors or lThe control switches 28 and |26) are respectively individually associated with the heating units IE) and IIB. Specifically, one terminal of the section is connected to the switching contact 26; one terminal of the section i2 is connected to the switching contact 24; and the common terminal of the sections and l2 is connected to the switching contact 22. Likewise, one terminal of the section is connected to the switching contact. |26; one terminal of the section ||2 is connected to the switching contact |24; and the common terminal of the sections and ||2 is connected to the switching contact |22. The switching contacts 2|, 23 and 25 are respectively connected to the N and conductors; and, likewise, the switching contacts |2|, |23 and |25 are respectively connected to the 1-, N and conductors.

As disclosed in the Andrews patent mentioned, when the off push button of the control switch is operated the six switching contacts thereof are operated to interrupt all electrical connections between the source of current supply and the associated heating unit; and the previously operated one of the other push buttons is returned to its normal position by the associated transfer and interlock mechanism. Thus only one of the push buttons of the control switch may occupy an operated or in position at any time, all of the other push buttons thereof occupying their normal or out positions. Also, in the control switch, when the high push button is operated, the two sections of the associated heating unit are connected in multiple across the and conductors; when the second push button is operated, one of the sections of the associated heating unit is connected across the and conductors; when the third push button is operated, the two sections of the associated heating unit are connected in multiple across the and N conductors; when the low push button is operated, the one section of the associated heating unit is connected across the and N conductors; and when the warm push button is operated, the two sections or the associated heating unit are connected in series across the and N conductors. In the above description it will be understood that the references and are employed only for the purpose of explanation as an alternating voltage actually appears between these line conductors. In the interest of brevity the specific operations of the control switches 20 and |20 selectively to effect the different heating connections between the source of current supply and the respective heating units il) and l0, will not be described; however, for reference purposes the sections and may be termed the rst sections of the respective heating units and IIE) and the sections |2 and ||2 may be termed the second sections of the respective heating units I!) and ||0 in employing the above description.

Further, the control circuit comprises a thermal control pot 3i) that includes a thermal element responsive to the temperature of a wall thereof and that is preferably of the construction disclosed in the copending application of Leo F. Berg and Walter R. McDowell, Serial No. 17,248, led on March 26, 1948, now patent No. 2,530,643, granted on November 21, 195|), and a timer 40 of conventional construction and arrangement. Also, the control circuit comprises a heating unit select key or switch 5c of the three-position type common to the heating units ll) and IIE), a thermal control select key or switch of the three-position type common to the control switches 2Q and |20, and timer control select key or switch l0 of the three-position type common to the control switches 2U and |26. The thermal control select key Eil is employed for the purpose of transferring either a low control or an off control from the thermal control pot 3U to the control switch of a selected one of the heating units IU or IID, as explained more fully hereinafter; while the timer control select key I8 is employed for the purpose of transferring either a low control or an off control from the timer 49 to the control switch of a selected one of the heating units or ||0, as explained more fully hereinafter. Of course, the, heating unit select key 59 is employed for the purpose of selecting one of the heating units I or I I0 to be controlled either by the thermal control pot 30 or by the timer 49 or by both the thermal control pot 30 and the timer 4U, as explained more fully hereinafter.

The control circuit further comprises a relay 80 individual to the thermal control pot 39, and a relay 90 individual to the timer 43, the relays 80 and 90 being employed for control purposes, as explained more fully hereinafter. Also, the control circuit is provided with two rectiiier bridges I3 and ||3 respectively individual to the heating units I0 and IIU, as well as two pilot or control lamps I4 and ||4 respectively individualto the heating units I9 and III). Further, the control circuit comprises two low electro-responsive motors 28 and |28 and two off electro-responsive motors 29 and |29, the motors 28 and 29 being also incorporated in the control switch 2), and the motors |28 and |29 being also incorporated in the control switch |26.

In the construction and arrangement of the electric range, it is contemplated that the control switches 29 and |29 will be mounted in corresponding openings provided in the upstanding hollow backsplasher, not shown, and readily manually operable from the front thereof. Also, it is contemplated that the timer 49 and the keys 50, 60 and 'I0 will be mounted in corresponding openings provided in the baoksplasher and readily manually operable from the front thereof. The casings of the control switches 2i) and |20, as well as the respectively associated motor pairs 28, 29 and |28, |29, are mounted within the hollow backsplasher and concealed from View from the front thereof. Likewise, the relays 88 and 90 and the rectifier bridges I3 and |I3 are mounted within the hollow backsplasher and concealed from View from the front thereof. Further, the pilot lamps I4 and H4 are suitably mounted in corresponding openings provided in the backsplasher and respectively associated with the opposite sides of the key B. The thermal control pot 38 may be readily and removably supported upon either one of the surface heating units I0 or IID and is connected by an associated cable 3| of the detachable type to a receptacle 32 also mounted upon the backsplasher and accessible from the front thereof.

Consider now the construction arrangement of certain of the elements of the control circuit in greater detail. The low motor 28 incorporated in the control switch 29 is in the form of a relay and comprises a winding the terminals of which are respectively connected to two conductors |3| and |32. Also, the low motor 28 comprises a pivotally mounted armature |33 that is operated when the winding thereof is energized and cooperates with a pin |34 carried by the push rod |35 o1 the associaated low push button. Thus when the winding of the low motor 28 is energized the armature |33 is operated to move the push rod |35, and consequently the low push button, through the pin |39 into its in position, whereby the control switch 29 is opera-ted into its low position just as though the low push button thereof had been manually operated from its out position into its in position. Similarly, the off motor 29 incorporated in the control switch 20 is in the form of a relay and comprises a winding the terminals of which are respectively connected to the conductor |32 and to a conductor |36. Also, the off motor 29 comprises a pivotally mounted armature |37 that is operated when the winding thereof is energized and cooperates with a pin |38 carried by the push rod |39 of the associated off push button. Thus when the winding of the oil motor 29 is energized the armature |31 is operated to move the push rod |39, and consequently the oi push button, through the pin |38 into its in position, whereby the control switch 29 is operated into its on` position just as though the off push button had been manually operated from its out position into its in position.

The low motor |28 incorporated in the control switch |29 is in the form of a relay and com-V prises a winding the terminals of which are respectively connected to two conductors |48 and |4I. Also, the low motor |28 comprises a pivotally mounted armature |42 that is operated when the winding thereof is energized and cooperates With a pin |43 carried by the push rod |44 of the associated low push button. Thus when the winding of the low motor |28 is energized the armature |42 is operated to move the push rod |44, and consequently the low push button, through the pin |43 into its in position, whereby the control switch |20 is operated into its low position just as though the low push button thereof had been manually operated from its out position into its in position. Similarly, the off motor |29 incorporated in the control switch |29 is in the form of a relay and comprises a winding the terminals of which are respectively connected to the conductor I4I and to a conductor |45. Also, the ofi' motor |29 comprises a pivotally mounted armature M6 that is operated when the winding thereof is energized and cooperates with a pin |41 carried by thc push rod |48 of the associated off push button. Thus when the winding of the off motor |29 is energized the armature |46 is operated to move the push rod |48, and consequently the off push button, through the pin |41 into its in position, whereby the control switch |20 is operated into its oi position just as though the oir push button had been manually operated from its out position into its in position.

The therniostatic control pot 50 constitutes a cooking vessel and comprises a detachable handle |49 that terminates adjacent the inner end thereof into a casing |50 thermally associated with the wall of the vessel and housing a thermostatic control or switch element I5| that is seiectively operated in accordance with the temperature of the contents of the vessel. The outer end of the handle |49 terminates in a connecting xture |52 that is adapted to receive a cooperating connecting fixture |53 that is carried by the inner end of the detachable connector or cable 3|, the outer end of the cable 3| being also provided with a connecting fixture |54 that cooperates with the receptacle S2 that is mounted upon the back:- spiasher, not shown, of the electric range. It will be understood that the inner end of the cable 3! may be readily connected and disconnected with respect to the outer end of the handle |49 of the pot 39 and that the outer end of the cable 3| may be readily connected and disconnected with respect to the receptacle 32. Finally, the receptacle 32 terminates two conductors |55 and It` that are employed for control purposes, as explained more fuly hereinafter. It will bc interval.

understood that when the contents of the vessel or pot 39 reach a predetermined temperature, or a predetermined cooking condition prevails in the vessel, the thermostatic element is operated to complete abridge acrossthe conductors |55 and |56 via the connecting fixtures |52, |53 and |54, and the receptacle 32. The temperature at which the thermal element |5| is operated may be adjusted manually by an associated adjusting screw indicated at |51.

The timer 48 comprises a manually operable control knob |58 readily accessible from the front of the backsplasher, not shown, from the front thereof that carries an associated index pointer |59 that cooperates with associated indicia |66. Thus manual rotation of the knob |58 effects the setting of a predetermined timing operation of the timer 4U as indicated by the pointer |59 cooperating with the indicia |66. A lso, the timer 4|) comprises an operating motor |6| of the synchronous type that is preferably a single phase Telechron motor. The operating motor |6| is provided with a circuit including a set of off-normal switch springs |62, one of the switch springs of the set |62 being connected to a conductor |63. The set of switch springs |62 is manually governed by the control knob |58, as indicated by the dotted line |62; the arrangement being such that the set of switch springs |62 occupies its open position when the control knob |58 occupies its zero time or oif position, and the set of switch springs |62 occupies its closed position when the control knob |58 occupies other than its off position. Thus when the control knob |58 is manually moved from its off position in order to set a predetermined timing operation of the timer 46 the set of off-normal switch springs |62 are closed connecting the conductor |63 to the operating motor |6| and subsequently when the operating motor |6| is operated the control knob |58 is returned back into its oi position during the set predetermined time, whereupon the set of switch springs |62 is again operated into its open position. Also, the timer 46 comprises a set of switch springs |64, the individual switch springs of which are respectively connected to two conductors |65 and |66 that are employed for a control purpose more fully explained hereinafter. The set of switch springs |65 is operatively connected to the control knob |58, as indicated by the dotted line |64; the arrangement being such that just as the control knob |58 is returned to its olf position the set of switch springs |64 is operated from its open position into its closed position and thence back into its open position, whereby the conductors |65 and |66 are bridged together for a short time Of course, the control knob |58 is operatively connected to the operating motor |6|, as indicated by the dotted line i6 The relay 80 is of the slow-to-operate type and comprises an upper low resistance winding |69 and a lower high resistance winding |16. The relay 89 may be rendered slow-to-operate by the provision of a low resistance shunting wind- .ing or slug on the field structure thereof, and furvwinding |68 is connected to one of the contacts |13; the other terminal of the lower winding |18 -i-s connected commonly to the conductor |55, to

one of thecontacts |13 and to one of the contacts |12; and the other contact |12 is connected to the conductor |56. One of the input terminals of the rectifier bridge 3 is directly connected to ground and the other input terminal thereof is directly connected to a conductor |14 that is commonly connected to one terminal of the section of the heating unit I0 and to the switching contact 26 of the control switch 28. One of the output terminals of the rectifier bridge I3 is connected to the conductor |32 and the other output terminal thereof is connected to a conductor |15. Also, a smoothing condenser |16 bridges the output terminals of the rectifying bridge |3. One of the contacts |1| is connected to the conductor |14, and the other contact |1| is connected to a conductor |11.

The relay 9|] is of the slow-to-operate type and comprises an upper low resistance Winding |16 and a lower high resistance winding |11. The relay 96 may be rendered slow-to-operate bythe pr-ovision of a low resistance shunting winding or slug on the field structure thereof, and further comprises an armature, not shown, that operates two sets of contacts |18 and |19, as explained more fully hereinafter. One terminal of the upper winding |16 and one terminal of the lower winding |11 are commonly connected to the conductor |14; the other terminal of the upper winding |16 is connected to one of the contacts |19; the other terminal of the lower winding |11 is connected commonly to the conductor |66, to one of the contacts |19 and to one of the contacts |18; and the other contact |18 is connected to the conductor |65. One of the input terminals of the rectifier bridge I3 is directly connected to ground and the other input terminal thereof is directly connected to a codnuctor |88 that is commonly connected to one terminal of the section of the heating unit and to the switching contact |26 of the control switch 29. One of the output terminal-s of the rectifier bridge ||3 is connected to the conductor |4| and the other output terminal thereof is connected to a conductor |8 Also, a smoothing condenser |82 bridges the output terminals of the rectifying bridge |3.

The key 56 comprises a normal middle position, a right-hand locking position selecting the first heating unit l5, and a left-hand locking position selecting the second heating unit I0. The righthand section of the key 56 comprises seven individual springs termed first, etc., from the right, and the left-hand section of the key 50 comprises seven individual springs termed eighth, etc., from the right. In the key 56, the rst spring terminates the conductor |36; the second spring terminates a conductor |83; the third spring terminates the conductor |3|; the fourth spring terminates a conductor |84; the fifth spring terminates the conductor |15; the sixth spring terminates a conductor |85; the seventh and eighth springs commonly terminate the conductor I'M; the ninth spring terminates a conductor |86; the tenth spring terminates the conductor i8! the eleventh spring terminates the conductor |86; the twelfth spring terminates the conductor |46; the thirteenth spring terminates the conductor |83; and the fourteenth spring terminates the conductor |45.

rhe key 6|) comprises a normal middle position, a right-hand locking position selecting the off motor 29 or the off motor |29 depending upon the position of the key 58, and a left-hand locking position selecting the low motor 28 or the low motor |28 depending upon the position of the Akey 56. The right-hand section of the key 60 comprises six individual springs termed first, etc., from the right, and the left-hand section of the key 60 comprises live individual springs termed seventh, etc., from the right. In the key 60, the first spring terminates the conductor |56; the second spring terminates the conductor |83; the third spring terminates the conductor |11; the fourth spring terminates the conductor |63; the fifth spring terminates the conductor |14; the sixth and seventh springs are jumpered together; the eighth spring terminates the conductor |63; the ninth spring terminates the conductor |11; the tenth spring terminates the conductor |56; and the eleventh spring terminates the conductor |84.

The key 10 comprises a normal middle position, an upper locking position selecting the low motor 28 or the low motor |28 depending upon the position of the key and a lower locking position selecting the off motor 23 or the off motor |29 depending upon the position of the key 50. The upper section of the key 1|) comprises two springs termed first and second from the top, and the lower section of the key comprises two springs termed third and fourth from the top. In the key 1D, the first spring terminates the conductor |84; the second and third springs are jumpered together and connected to the conductor |65; and the fourth spring is connected to the conductor |83.

The connection and arrangement of the control circuit incorporated in the electric range will best be understood from the following examples of the different operations thereof under the control of the thermal pot 30 and the timer 40 after a manual setting of one of the control switches or |20 depending upon the selected heating unit I0 or I0. First assuming that the keys 5U, 60 and 10 occupy their normal middle positions and that the control switches 20 and |20 occupy their off positions, all of the electric circuits are open. At this time the heating of the first surface unit I0 may be governed entirely manually by appropriate manipulation of the push buttons of the associated control switch 20; and, likewise, the heating of the second surface unit ||0 may be governed entirely manually by appropriate manipulation of the push buttons of the associated control switch |20.

Now assuming that a control is to be exercised only by the thermal pot 30, the connector or cable 3| is operatively connected between the handle |49 of the pot 30 and the receptacle 32 provided in the backsplasher, not shown, of the electric range; and the food to be cooked is placed in the vessel or pot 39. At this time the user decides which of the heating units I0 or ||0 that is to be employed and operates the select key 50 to the corresponding position. Similarly, the user decides whether the thermal pot is to operate the control switch of the selected heating unit to its low position or to its off position when the pot 30 reaches the previously set cooking condition therein, and operates the select key 68 to the corresponding position.

As an example, assume that the user wishes to employ the first heating unit l0 for the purpose of heating the pot 39 and that the control switch 20 is to be operated from its high position to its low position when the contents of the pot 30 reach the previously set temperature, the select key 50 is operated to its right-hand locking position and the select key 60 is operated to its left-hand locking positiion. At this time the pot containing the food to be cooked is placedv upon the first heating unit l0 and the high push button of the control switch 28 is operated, whereby the rst heating unit ||3 is heated in the manner previously explained at the high rate effecting heating of the supported pot 343 and its contents.

When the predetermined cooking temperature is reached in the pot Sii, normally when the contents of the pot 35 begin to boil, the thermostatic element |5| is operated to bridge the conductors |55 and |56, thereby completing a circuit for energizing in multiple the upper and lower windings of the relay 8G and a series circuit for energizing the winding of the low motor 28. Specifically, when the control switch 2li is operated into its high position, an alternating voltage is applied to the conductor |14 at the switching contacts 2B in the control switch 28, whereby the input terminals of the rectifying bridge I3 are supplied with alternating current power causing a direct current voltage to appear between the output terminals thereof so that the pilot lamp I4 is directly illuminated via a circuit including the conductors H5 and |85 and the fifth and sixth springs of the key At thisI time the positive output terminal of the rectifying bridge I3 is connected via the conductor |32, the winding of the low motor 28, the conductor |3|, the third and fourth springs of the key 50, the conductor |813, and the tenth and eleventh springs of the key 60 to the conductor |56, the conductor |56 is bridged to the conductor |55 by the thermal element |5I; the conductor |55 is connected directly via the lower winding |16 of the relay to the conductor |14', and the conductor |55 is connected via the contacts |13 and the upper winding |69 of the relay 80 to the conductor |14; and the conductor |14 is connected via the fifth, sixth and seventh springs of the key 50 and the conductor |15 to the negative terminal of the rectifying bridge I3. When this series circuit is l thus completed, the low motor 28 operates to operate its armature |33, whereby the low push button of the control switch 28 is operated so that heating of the heating unit I8 continues at the low rate. Also, shortly after this series circuit is thus completed the relay 80 operates, it being of the slow-to-operate type. Upon operating, the relay 80 interrupts, at the contacts |13, the circuit for energizing the upper winding thereof; and completes, at the contacts |12, a bridge path in multiple to the thermal element |5|. Accordingly, at this time a holding circuit is completed for energizing the lower winding |18 of the relay 4 80 in series with the winding of the low motor 28; which holding circuit includes the conductor |32, the winding of the low motor 28, the conductor |3|, the third and fourth springs of the key 50, the conductor 84, the tenth and eleventh springs of the key Si?, the conductor |58, the contacts |12, the lower winding |10 of the relay 80, the conductor |14', the fifth, sixth and seventh springs of the key 58 and the conductor |15. Thus at this time the thermostatic element |5| is disabled; and when the above-traced holding circuit unit I is disconnected from the associated source of current supply and power is removed from the conductor` |14. Thus the pilotd lamp I4 is extinguished, and the previously traced holding circuit for energizing the winding of the low motor 28 in series with the lower winding |10 of the relay 80 is interrupted in order to cause the relay 80 to restore, the low motor 28 having already released its armature |33, as previously explained. Upon restoring, the relay 80 interrupts, at the contacts |12, a further point in the holding circuit for energizing the lower winding thereof; and reprepares, at the contacts |13, the operating circuit for energizing in multiple the upper and lower windings |69 and |13 of the relay 80. At this time the control of the heating of the first heating unit I0 has been completed, and ordinarily the select keys 50 and 69 are returned to their normal middle positions.

As another example, assume that the user wishes to employ the rst heating unit I0 for the purpose of heating the pot 30 and that the control switch 20 is to be operated from its high position to its ofi position when the contents of the pot 30 reach the previously set temperature, the select key 50 is operated to its righthand locking position and the select key 69 is operated to its right hand locking position. At this time the pot containing the food to be cooked is placed upon the rst heating unit I0 and the high push button of the control switch 29 is operated, whereby the rst heating unit I0 is heated in the manner previously explained at the high rate effecting heating of the supported pot 30 and its contents.

When a predetermined cooking temperature is reached in the pot 36, normally when the contents of the pot 3|! begin to boil, the thermostatic element |5| is operated to bridge the conductors |55 and |56, thereby completing a circuit for energizing in multiple the upper and lower windings of the relay 80 and a series circuit for energizing the winding of the off motor 29. The operating circuit mentioned extends from the conductor |32 via the winding of the off motor 29, the conductor |36, the iirst and second springs of the key 59, the conductor |83, and the iirst and second springs of the key 60 to the conductor |56; the conductor |56 is bridged to the conductor |55 by the thermal element I5I; the conductor |55 is connected directly via the lower Winding |16 of the relay 80 to the conductor |14 and the conductor |55 is connected via the contacts |13 and the upper winding |69 of the relay 80 to the conductor 114'; and the conductor |14' is connected via the fth, sixth and seventh springs of the key 50 to the conductor |15. When this series circuit is thus completed, the o motor 29 operates to operate its armature |31, whereby the off push button of the control switch 2|! is operated' so that heating of the heating unit Ill is discontinued. When the control switch 20 is thus operated into its off position the supply of power via the conductor |14 to the rectifying bridge I3 is interrupted so that the lpilot lamp I4 is extinguished and the above-traced operating circuit is interrupted prior to operation of the relay 80. Thus the relay 80 is not operated, and the off motor 29 releases its armature |31 in order to prevent interference with subsequent manual operation of the control switch 20. At that time the control of the heating of the first heating unit I0 has been completed, and ordinarily the select keys 50 and 69 are (returned to their normal middle positions.

Now assuming that a control is to be exercised only by the timer 49, it is unnecessary to connect the cable 3| between the outer end of the handle |49 of the pot 30 and the receptacle 32 supported on the front of the backsplasher, not shown, of the electric range. In fact, it is not even necessary to employ the thermal pot 30 in the cooking operation as any vessel may be used to contain the food that is to be cooked. At this time the user decides what time interval the food contained in the vessel is to be cooked and manually operates the knob |58 in accordance with the time noted, the pointer |59 indicating the time selected due to its cooperation with the indicia |60. Next, the user determines which of the heating units I9 or ||0 that is to be employed and operates the select key 50 to the corresponding position. Similarly, the user decides whether the timer 40 is to operate the control switch of the selected heating unit to its low position or to its off position when the timer 40 operates through the preset time interval, and operates the key 16 to the corresponding position. l

As an example, assume that the user wishes to employ the rst heating unit IE) for the purpose of heating the vessel and that the control switch 20 is to be operated from its high position to its low position at the expiration of the timing interval by the timer 40, the select key 5|) is operated to its right-hand locking position and the select key 10 is operated to its upper locking position. At this time the vessel containing the food to be cooked is placed upon the first heating unit I9 and the high push button of the control switch 20 is operated, whereby the first heating unit I0 is heated in the manner previously explained at the high rate eiecting heating of the supported vessel and its contents.

When the'control switch 26 is thus operated into its high position, power is supplied to the rectifying bridge I3 effecting illumination of the pilot lamp I4, as previously explained. Also, power is supplied directly via the conductor |14, the fifth, sixth, seventh and eighth contacts of the select key 60, the conductor |63, and the ofinormal switch springs |62 to the operating motor |6| of the timer 40, whereby the timer 40 initiates the previously set timing operation, the operating motor I6! operatingr at the synchronous timing rate, as previously explained. Upon the expiration of the previously set timing operation of the timer 49 the set of switch springs |62 is operated back into its open position interrupting the circuit for the operating motor I6I in order to arrest further operation of the timer 49; Also at this time the control knob |58 of the timer 40 has been operated back into its zero time or normal position and the set of switch springs |64 is operated from its open position into its closed position and thence back into its open position, the set of switch springs |64 being retained in its closed position for a time interval suiciently long to permit operation of the slowto-operate relay 90, as explained more fully below.

More particularly when the set of switch springs |64 is operated into its closed position. there is completed a circuit for energizing in multiple the upper and lower windings of the relay and a series circuit for energizing the winding of the low motor 28. This circuit includes the conductor |32, the winding of the low motor 28, the conductor |3I, the third and fourth springs of the key 50, the conductor |84, the first and second springs of the key 10. the

conductor |65, the set of switch springs |64, and the conductor I 66 the conductor |66 is connected directly via the lower winding |11 of the relay 90 to the conductor |14', and the conductor |66 is connected via the contacts |19 and the upper winding |16 of the relay 90 to the conductor |14; and further, the conductor |14' is connected via the fifth, sixth and seventh springs of the key 50 to the conductor |15. When this series circuit is thus completed the low motor 28 operates to operate its armature |33, whereby the low push button of the control switch 20 is operated so that heating of the heating unit I continues at the low rate. Also, shortly after this series circuit is thus completed the relay 90 operates, it being of the slow-to-operate type. Upon operating, the relay 90 interrupts, at the contacts I 19, the circuit for energizing the upper winding thereof; and completes, at the contacts |18, a bridge path in multiple to the set of switch springs |64 of the timer 40. Accordingly, at this time a holding circuit is completed for energizing the lower winding |11 of the relay 90 in series with the winding of the low motor 28; which holding circuit includes the conductor |32, the winding of the low motor 28, the conductor |3|, the third and fourth springs of the key 50, the conductor I 84, the first and second springs of the key 10, the conductor |65, the contacts |18, the lower winding |11 of the relay 90, the conductor |14', the fifth, sixth and seventh springs of the key 50, and the conductor |15. Thus at this time the set of switch springs |64 of the timer 40 is disabled; and the subsequent operation of the set of switch springs |64 into its open position is without effect; and when the above-traced holding circuit is completed the relay 90 is retained in its operated position. However, the low motor 28 releases its armature 33 due to the high series resistance of the lower winding |11 of the relay 90 in order to prevent the low motor 28 from interfering, in any way, with subsequent manual operation of the control switch 20.

Subsequently, after the contents of the vessel have been cooked through a time interval agreeable to the user the 01T push button of the control switch 20 is operated, whereby the first heating unit I0 is disconnected from the associated source of current supply and power is removed from the conductor 14. Thus the pilot lamp 4 is extinguished, and the previously traced holding circuit for energizing the winding of the low motor 28 in series with the lower winding |11 of the relay 90 is interrupted in order to cause the relay 90 to restore, the low motor 28 having already released its armature |33, as previously explained. Upon restoring, the relay 90 interrupts, at the contacts |18, a further point in the holding circuit for energizing the lower winding thereof; and reprepares, at the contacts I 19, the operating circuit for energizing in multiple the upper and lower windings |16 and I 11 of the relay 90. At this time the control of the heating of the iirst heating unit I0 has been completed, and ordinarily the select keys 50 and are returned to their normal middle positions.

In passing it is noted that in the timer 40 a gong |90 may be provided that is operatively connected to the knob |56, as indicated by the dotted line |9; the arrangement being such that when the knob |58 is returned back into its zero time or normal position that the gong |90 is sounded. This arrangement gives the user of 14 the electric range an audible alarm or signal indicating that the timer 40 has completed its previously set timing operation.

As another example, assume that the user wishes to employ the rst heating unit IU for the purpose of heating the vessel and that the control switch 26 is to be operated from its high position to its oi position at the expiration of the previously set timing operation of the timer 48, the select key 5G is operated to its right-hand locking position and the select key 10 is operated to its lower locking position. At this time the vessel containing the food to be cooked is placed upon the iirst heating unit lil, and the high push button of the control switch 20 is operated, whereby the first heating unit Ii) is heated in the manner previously explained at the high rate effecting heating of the supported vessel and its contents.

When the control switch 20 is thus operated into its high position, power is supplied to the rectifying bridge I3 eiecting illumination of the pilot lamp |4, and the circuit of the operating motor ISI is completed initiating operation of the timer 4t, as previously explained. Upon the expiration of the previously set timing operation of the timer 46 the set of switch springs |62 is operated back into its open position interrupting the circuit for the operating motor ISI in order to arrest further operation of the timer 40. Also,

at this time the control knob |58 of the timer 43 has been operated back into its zero time or normal position and the gong is sounded in order to inform the user that the timer 40 has completed its timing operation, as previously explained. Also, at this time the set of switch springs 64 is operated from its open position into its closed position and thence back into its open position, whereby there is completed a circuit for energizing in multiple the upper and lower windings of the relay 90 and a series circuit for energizing the winding of the oi motor 29. The operating circuit mentioned extends' from the conductor |32 via the windings of the off motor 29, the conductor |36, the rst and second springs of the key 50, the conductor |83, and the third and fourth springs of the key 10 to the conductor |65; the conductor |65 is bridged to the conductor |66 by the set of switch springs |64; the conductor |65 is connected directly via the lower winding |11 of the relay 90 to the conductor |14', and the conductor |66 is connected via the contacts |19 and the upper winding |16 of the relay S!) to the conductor |14; and the conductor |14 is connected via the fifth, sixth and seventh springs of the key 50 to the conductor |15. When thisl series circuit is thus completed, the orf motor 29 operates to operate its armature |31, whereby the off push button of the control switch 2li is operated so that heating of the heating unit ID is discontinued. When the control switch 20 is thus operated to its oi position the supply of power via the conductor |14 to the rectifying bridge I3 is interrupted so that the pilot lamp I4 is extinguished, and the above traced operating circuit is Yintrrupted prior to operation of the relay 9D. Thus the relay 90 is not operated, and the off motor 29 releases its armature I 31 in order to prevent interference with subsequent manual operation of the control switch 20. At this time the control of the heatf ing of the rst heating unit I0 has been cornpleted, and ordinarily the select keys 50 and 10 are returned to their normal middle positions.

Now assuming that controls are to be exercised 15 jointly by the thermal pot 30 and by the timer 40, the pot 30 is connected up as previously explained, and the food to be cooked is placed in the pot 30. Again the user decides which of the heating units I or ||0 that is to be employed and operates the select key 50 to the corresponding position, and again it is assumed that the key 50 is operated to its righthand locking position to select the first heating unitI I0. Then the user operates the select key 69 to its lefthand locking position in order to give the thermal pot 30 control of the operation of the control switch 20 from its high position into its low position. Then the user operates the select key .19 into its lower locking position in order to give the timer 40 control of the operation of the control `switch 20 from its low position into its oif position. The user then sets the desired operating time of the timer 40 by appropriate manipulation of the knob |58, and places the pot 30 and its contents upon the first heating unit I0. Finally, the user operates the high push button of the control switch 20, whereby the rst heating unit I0 isV heated in the manner previously explained at the high rate effecting heating of the supported pot 30 and its contents.

When the pot 30 and its contents reach the predetermined cooking temperature, the thermal element is operated closing the previously traced operating circuit for energizing in multiple the upper and lower windings of the relay 80 and the winding of the low motor 28, whereby the low motor 28 operates its armature |33 in order to operate the control switch 2|) from its high position into its low position so that heating of the pot 30 and its contents continues at the low rate. Shortly thereafter the relay 80 operates interrupting the circuit for energizing the upper winding thereof and completing the holding circuit independent of the thermal element |5| for energizing the lower Winding of the relay 80 in series with the Winding of the low motor 28, as previously explained. The relay 80 is retained in its operated position and the low motor 23 releases its armature |33 so as to prevent interference with subsequent operation of I the control switch by the oc motor 29.

. Also, upon operating, the relay 89 completes, at the contacts |1|, an alternative circuit for the operating motor |6| of the timer 40 that includes the conductors |14 and |11, the eighth and ninth springs of the key 69 and the conductor |63, whereby operation of the operating motor Vpot 30 has reached its Apredetermined cooking temperature.

Heating of the pot 30 and its contents continues at the low rate until the expiration of the preset time interval, whereby the timer 49 operates the set of switch springs |64 in order to complete the circuit for energizing in multiple the upper and lower windings of the relay 9D and the series circuit for energizing the wind- Aing of the oi motor 29. The oi motor `29 then -16 operates its armature |31, whereby the control switch 20 is operated from its low position into its off position so that the supply of power to the rectifying bridge I3 is interrupted. At this time the pilot lamp M is extinguished, the holding circuit for retaining operated the relay is interrupted and the circuit for energizing in multiple the upper and lower windings of the relay 99 is interrupted. Thus the relay 80 restores and the relay 9i! does not operate as it'4 is of the slow-to-operate type. The circuits for energizing the windings of the low motor 28 and the oi motor 29 are interrupted so that there is no interference by the motors 28 and 29 with subsequent manual operation of the control switch 20. At this time the control of the heating of the first heating unit i0 has been completed, and ordinarily the select keys 59, 6E) and 10 are returned to their normal middle positions.

In the foregoing examples of the various operations of the control circuit it was always assumed that the user selected the rst heating unit I0 to be controlled; however, it will be understood that the second heatingunit l0 may be selected for control in a substantially identical manner by operation of the select key 50 to its left-hand locking position. The control that is exercised upon the second Vheating unit ||0 depends upon the selective operations of the select keys 60 and 10, whereby the elements of the control circuit are operative in a manner substantially identical to that previously described to efectthe required control of the `second heating unit ||0. In the interest of brevity the details of the operations of the control circuit to carry out the individual controls of the heating of the second heating unit H0 will not be set forth, as these operations are substantially the same as those described in conjunction with the first heating unit l0. Thus it will be understood that the thermal pot 30 may be supported upon the second heating unit H9 and employed to operate either the low motor |28 or the oi motor |29 depending upon the position of the select key 60. as previously explained. Likewise, the timer 40 may be employed to operate either the low motor |28 or the off motor |29 depending upon the position of the select key 10, as previously explained. Finally, the low motor |28 and the off motor |29 may be sequentially controlled respectively by the thermal pot 39 and by the timer 40 by operating the select key 60 into its left-hand locking position and by operating the select key 10 into its lower locking position. In this arrangement, when the select key 50 occupies its left-hand locking position selecting the second heating unit |||l to be controlled, the control switch E29 controls the supply of power via the conductor |89 to the rectifying bridge ||3 just as the control switch 20 controls-the supply of power via the conductor |14 to the rectifying bridge I3. Also, in this case the power for operating the relays 89 and 99 and the motors |28 and |29 is supplied from the rectifying bridge ||3 instead of the rectifying bridge I3. Finally in this case the pilot lamp ||4 is illuminated when power is supplied to the rectifying bridge ||3.

In the foregoing illustration the thermostatic pot 30 or the timer 49 or both the thermostatic pot 3|! and the timer 49 were selectively employed for the purpose of controlling the motors 28 and 29 associated with the control switch 20 or the motors |28 and |29 associated with the control switch 12u. while the motors 2s and Iza are operatively associated with the low push but- .tons of the control 4switches 20 and |29, and While the motors 29 and |29 are operatively associated with the off push buttons of the control switches 20 and |20, it is contemplated that the set of motors in any control switch maybe operatively associated with any desired two of the push .buttons incorporated therein. By way of illustration in the control switch '20 the two motors 28 and 29 may be operatively associated with .the respective second and warm ,push'buttons incorporated therein, whereby the corresponding switching positions of the control switch 20 are obtained incident tothe respective operations of the motors 28 and '29. A wide variety of arrangements may be readily obtained by appropriate .association of .the motors '28 and 29 with the push rods of the desired push buttons incorporated in the contrlswitch 20 as twill be readily understood from a mechanical standpoint upon examination of the physical construction and arrangement of the push button control switch 20, as disclosed in the previously mentioned McDowell application.

In view of the foregoing it is apparent that therehas been provided an improved and exceedingly flexible heating control circuit'for a heat- .ing appliance, such, for example, as an lelectric range.

"While there has been described what is at present considered to be the `preferred embodiment 'of the invention, it will be understood that various modifications may be made therein, and it is'intended to cover in the appended claims Vallsuch modifications as fall'within'the true spirit and scope of invention.

'What is claimed is:

'1.'In an appliance including a heating unit, ya source of current supply, anda unitary manually operable control switch selectively operative into a plurality of different positions in 'order Ato establish a corresponding plurality'of `different electrical heating Aconnections lbetween said `heating unit and Vsaid source so as to effect heating of rsaid heating unit at corresponding different heating rates; the combination comprising aJ rst electro-responsive motor operative'to 'operate said switch into a first of its positions, a iirst operating circuit for said rst'motor, a second electroresponsive motor operative to operate said-switch into'a second'of its positions,a second operating circuit forsaid second motor,means for selecting either one of said operating circuits, means'responsivev to operation of'saidswitch into a third of its positions for preparing the'selected one-of lsaid operating circuitsa selectivelyy operative device, and means responsive tooperation oil-said device for completing the selected `and prepared one of said operating circuits.

2. In a cooking appliance including a heating unit adapted to support a cooking Ivessel, a source of current supply, and a unitary manually oper- 'able control switch selectively operative from an `ofi position into'respective high and-lowV posi- 'tions to complete respective high' and low electrical heating connections betweensaid heating unit "and said source so as to 'eiect heating lof ysaid heating unit at corresponding highandlow sai'dsecondmotonmeans dor selecting either one of said voperating circuits, means responsive to operation of said switch into `its high position for preparing `the selected one of said operating circuits, a device operatedin response to a predetermined .cooking temperature of a wall of a cooking .vessel supported by said heating unit, and means responsive to operation of Vsaid device for completing the selected andprepared one of said operating circuits.

3. Invan appliance including a heating unit, .a source of current supply, and a unitary manually operable control switch of the push button type provided Iwith a plurality of individual push buttons selectively operative in order to operate said switch into a corresponding yplurality lof different Vpositions ,to establish a corresponding `plurality of Ydierentelectrical heating connections between said heating .unit and said source sofas as to eirect heating of said heating unit at a corresponding plurality of different'he-ating rates; the combination comprising a first electro-responsive motor opera-tively associated with a irst of said push buttons and operative to operate said rst Vpush button, a rst operating `circuit for saidirst motor, a second electro-responsive motor operatively associated with a lsecond of said push buttons and operative to operate said second push button, -a second operating circuit for said second motor, means for selectingeither one of said operating circuits, means responsive to operation of athird `of said push buttons for preparing the selected one of said operating circuits, a selectively operative device, and means responsive to operation of said `device vfor completing the selected and prepared one of said operating circuits.

4. In anappliance including a heating unit, a source of current supply,rand a unitary manually operable control switch selectively operative into a Aplurality of different positionsin order to establish ya corresponding plurality of different electrical heating connectitons between said heating unitand said source so as to effect heating of said heating unit at corresponding different heating rates; the combination comprising a first electro-responsive motor operative to operate said switch into afirst of Vits positions. a ilrst operating circuit for said rst motor, a second electro-responsive motor operative to operate said switch into a second of Aits positions, a,sec ond operating circuit for said second motor, means for selecting either oneof said operating circuits, means responsive to operation of said switch into a third of its positions for preparing the selected one of said operating circuits, aidevice of the thermal operatedf'type Ygovernedby said heating unit, and meansresponsive to-operation of said device for completing lthe Selected and prepared one of said operating circuits.

5. In an appliance including a heating unit, a

source of current supply, and a unitary manually operable control switch selectively operative into a plurality of kdiiiierentpositions in ordervto establish a corresponding Vplurality of different electrical heating connections between saidheating unit andrsaid source so asto effect heating of said heating unit at Ycorresponding diiferent heating rates; the combination comprisinga firs-t electro-responsive'anotor operative to operatensaid switch into a rst of its positions, a rst operating circuit for said iirst motor, Y:a second velectroresponsive motor operative to operate said switch into a second of its positions, asecond operating circuit for vsaid second motor, -means for selecting either one of said operating'circuits, means .responsive to operation-'offsaid switch intoa third assisi@ lof its-positions for preparing the selected one of said. operating circuits, a device of the time operated type governed by clock mechanism, and means responsive to operation of said device for completing the selected and prepared one of said operating circuits.

6; In an appliance including a heating unit, a source of current supply, and a unitary manually operable control switch selectively operative into aplurality of different positions in order to establish a corresponding plurality of different electrical heating connections between said heating unit and said source so as to effect heating of vsaid heating unit at corresponding different heating rates; the combination comprising a first electro-responsive motor operativev to operate said switch into a first of its positions, a first operatingv circuit for. said first motor, a second electro-responsive motor operative to operate said switch into a second of its positions, a second operating circuit for said second motor, means for selecting either one of said operative circuits, means responsive to operation of said switch into a third of its positions for preparing the selected one of said operating circuits, a first device of the thermal operated type governed by said heating unit, a second device of the time operated type governed by clock mechanism, means for selecting either one of said devices, and means responsive to operation of the selected one of said devices for completing the selected and prepared one of said operating circuits.

'7. In an appliance including a heating unit, a source of current supply, and a unitary manually operable control switch selectively operative from an off position into respective high and low positions to complete respective high and low electrical heating connections between said heating unit and said source so as to effect heating of said heating unit at corresponding high and low heating rates; the combination comprising a first electro-responsive motor operative to operate said switch into its low position, a iirst operating circuitv for said first motor, a second electroresponsive motor operative to operate said switch into its oi position, a second operating circuit for said second motor, a device of the thermal operated type governed by said heating unit, a timer, means responsive to operation of said switch into its high position for preparing said first .operating circuit, means responsive to operation of said device for completing said prepared first operating circuit and for preparing said second operating circuit and for initiating a timing operationof said timer, and means responsive to completion of a predetermined timing operation of said timer for completing said prepared second operating circuit.

8..In an appliance including first and second heating units, a source of current supply, a first unitary manually operable control switch individually associated with said first heating unit,

and a second unitary manually operable control switch individually associated with said second heating unit, each of said switches being Selectivelyoperative into a plurality of diiferent positions. in order to establish a corresponding plurality of different-electrical heating connections between the individually associated one of said heating units and said source so as to effect heating of the individually associated one of said heating units at corresponding different heating rates; the combination comprising a first electroresponsive motor operative to operate said first switch into a given one of its positions, a first operating circuit for said first motor, a second electro-responsive motor operative to operate said second switch into a given one of its positions, a second operating circuit for said second motor, means for selecting either one of said operating circuits, means responsive to operation of said first switch into a predetermined one of its positions for preparing said first operating circuit, means responsive to operation of said second switch into a predetermined one of its positions for preparing said second operating circuit, a selectively operative device, and means responsive to operation of said device for completing the selected and prepared one of said operating circuits.

9. In an appliance including first and second heating units, a source of current supply, a first unitary manually operable control switch individually associated with said first heating unit, and a second unitary manually operable control switch individually associated with said second heating unit, each of said switches being selectively operative into a plurality of different positions in order to establish a corresponding plurality of diierent electrical heating connections between the individually associated one of said heating units and said source so as to effect heating of the individually associated one of said heating units at corresponding different heating rates; the combination comprising a first electroresponsive motor operative to operate said first switch into a given one of its positions, a first operating circuit for said first motor, a second electro-responsive motor operative to operate said second switch into a given one of its positions, a second operating circuit for said second motor, means for selecting either one of said operating circuits, means responsive to operation of said first switch into a predetermined one of its positions for preparing said first operating circuit, means responsive to operation of said second switch into a predetermined one of itsrpositions for preparing said second operating circuit, a device of the thermal operated type adapted to be associated with either one of said heating units and governed by the associated one of said heating units, and means responsive to operation of said device for completing the selected and prepared one of said operating circuits.

10. In an appliance including iirst and second heating units, a source of current supply, a first unitary manually operable control switch individually associated with said rst heating unit, and a second unitary manually operable control switch individually associated with said second heating unit, each of said switches being selectively operative into a plurality of different positions in order to establish a corresponding plurality of different 'electrical heating connections between the individually associated one of said heating units and said source so as to effect heating of the individually associated one of said .heating units at corresponding different heating rates; `the combination comprising a rst electroresponsive motor operative to operate said first switch into a givenone of its positions, va first operating circuit for said first motor, a second electro-responsive motor operative to operate said second'switch into a given one of its positions, a secondoperating circuit for said second motor, meansfor selecting either one of said operating circuits, means responsive to operation of vsaid first-switch into a predetermined one of 4its positions for preparing Asaid first operating circuit, `means responsive to' operation of said switch into a vpredeternline-d Vone of its vheating unit, each of said switches being selectively operative into a plurality of different positions in order to establish a corresponding plurality of different 'electrical heating connections between the individually associated one oi said heatingpunits and said source so as to' effect heating of the individually associated one of said heating units at corresponding different heating rates; Vfirst and second electro-responsive motors operatively associated with said first switch and respectively operative to operate said iirst switch into rstp and second of its positions, a iirst and second operating circuits for said rst and second motors respectively, means responsive to operation of said first switch intoA a third of its positions for preparing said rst and second.

operating circuits,A third Vand fourth electroresponsive motors operatively associated with said second switch and respectively operative to operate said second switch into first and second of its position, third and fourth operating circuits for said third and fourth motors respectively, means responsive to operation of said second switch into a third of its positions for preparing said third and fourth operating circuits, means for selecting any one of said operating circuits, a selectively operative device, and means responsive to operation of said device for completing the selected and prepared one of said operating circuits.

12. In an appliance including a heating unit, a source of current supply, and a unitary manually operable control switch selectively operative from an ofi position into respective high and low positions to complete respective high and low electrical heating connections between said heating unit and said source so as to effect heating of said heating unit at corresponding high and low heating rates; a thermal device, a timer, a con- Vtrol device, a first electro-responsive motor operative to operate said switch from its high position into its low position, a first operating circuit for said first motor, a second electro-responsive motor operative to operate said switch from its low position into its oii position, a second operating circuit for said second motor, means governed bysaid thermal device in response to a predetermined heating effect produced by said heating unit following manual operation of said switch from its oi position into its high position for completing said rst operating circuit and for operating said control device, means responsive to operation of said control device for initiating a timing operation of said timer, and means governed by said timer in response to the completion of a predetermined timing operation thereof for completing said second operating circuit.

13. In an appliance including a heating unit, a source of current supply, and a unitary manually operable control switch selectively operative into a ,plurality of different positions in order to es- Ytabl'ish `a corresponding pluralityV of different electrical heating connections between said 4heating unit and said sourceso as to effect heating of said heating unit at corresponding different heating rates; the combination comprising a first electro-responsive Y.motor operative to operate said switch into a first of its positions, Aa rst operating circuit for said first motor, a'second electro-responsive motor operative to operate said switch into a second of its positions, va second operating circuit for said secondmotor, means for selecting either one of said operating circuits, means responsive to Voperation of 'said switch into a third of its positions forpreparing the selected one of said operating circiuts, a

selectively operative device,yslowacting mechanism, Ameans -responsive to operation of said device for completing the selected and prepared one of 'said operating circuits in order to operate the associated one of said motors and for initiating operation of said mechanism, and means responsive to complete operation of said mechanism for interrupting the completed one of said operating circuits in order to restore the associated one of said motors.

14. In an appliance including a heating unit,

a source of current supply, and a unitary manur'tojestablish a corresponding plurality of diiernt electrical heating connections between said heating unit and said source so as to effect heating of said heating unit at corresponding different heating rates; the combination comprising a iirst electro-responsive motor operative to operate said switch into a first of its positions, a iirst operating circuit for said first motor, a second electro-responsive motor operative to operate said switch into a second of its positions, a second operating circuit for said second motor, means for selecting either one of said operating circuits, means responsive to operation of said switch into a third of its positions for preparing the selected one of said operating circuits, a rst device of the thermal operated type governed by said heating unit, a second device of the time operated type governed by clock mechanism, means for selecting either one of said devices, slow-acting mechanism, means responsive to operation of the selected one of said devices for completing the selected and prepared one of said operating circuits in order to operate the associated one of said motors and for initiating operation of said mechanism, and means responsive to complete operation of said mechanism for interrupting the completed one of said operating circuits in order to restore the associated one of said motors.

15. InI an appliance including a heating unit, a source of current supply, and a unitary manually operable control switch selectively operative from an off position into respective high and low positions to complete respective high and low electrical heating connections between said heating unit and said source so as to effect heating of said heating unit at corresponding high and low heating rates; the combination comprising a first electro-responsive motor operative to operate said switch into its low position, a first operating circuit for said rst motor, a second electroresponsive motor operative to operate said switch into its off position, a second operating circuit for said second motor, means responsive to operation of said switch into its high position for preparing said first operating circuits, a device of the thermal operated type governed by said heating unit. a timer, slow-acting mechanism, means responsive to operation of said device for completing said first operating circuit in order to operate said first motor and for initiating operation of said mechanism and for initiating a timing operation of said timer, means responsive to complete operation of said mechanism for interrupting said rst operating circuit in order I source of A. C. supply, and a unitary manually operable control switch selectively operative from an oi position into respective high and low positions to complete respective high and low electrical heating connections 'between said heating unit and said source in order to eiect heating of said heating unit at corresponding high and low heating rates; the combination comprising a rectifier having input and output terminals,

means responsive to operation of said switch out of its oi position for connecting said source to the input terminals of said rectifier and responsive to operation of said switch into its off position for disconnecting said source from the input terminals of said rectier, an electro-responsive motor having a winding and operative to operate said switch into a given one of its positions, a selectively operative device, and means responsive to operation of said device for connecting the winding of said motor to the output terminals of said rectier, the winding of said motor being energized when it is connected to the output terminals of said rectier only when said source is connected to the input terminals of said rectifier, said motor being operated in response to energization of the winding thereof.

WALTER R. MCDOWELL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,682,337 Hewitt Aug.` 28, 1928 .1,702,480 Newsom Feb. 19, 1929 2,222,124 Sherman Nov. 19, 1940 2,327,632 Frazier Aug. 24, 1943 2,363,326 Hodgkins Nov. 21, 1944 2,385,433 Weber Sept. 25, 1945 2,385,434 Weber Sept. 25, 1945 2,409,414 Bletz Oct. 15, 1946 2,421,452 Cody June 3, 1947 2,431,904 Andrews Dec. 2, 1947 2,530,643 Berg et al Nov. 21, 1950 2,559,579 McDowell Apr. 24, 1951 

